It seems like there is a lot of mileage and shorter, borderline anaerobic work, but not really anything in between. Outside of the 15 at MP, your longest rep is 6 minutes. I would add a lot more grinding tempos if I were you. You don't need to run 4:15 for any of the miles in your marathon. Also, you've got a big taper prior to Columbus half (which I assume you are racing hard). Racing it is fine 8 weeks out, but you've lost a lot of opportunities for training stimulus with the taper and then recovery.
I would supplant some of the shorter speed work with more grinding tempos with harder finishes. Something like 8 miles at 5:20, 2 miles at 4:55. Or 12 miles with the first 6 at 5:30, last 6 at 5:15.